This invention relates generally to video signals and particularly to means for compressing video white signals and improving their transient response.
Video enhancement techniques have been used for many years to improve the display characteristics of video signals on cathode ray tubes (CRTs). Due to the limitations on electron beam focusing or spot size control in CRTs, peak white signals have an annoying tendency to cause "blooming" (defocusing) of the electron beam which can seriously degrade the display. Prior art techniques have been used to control blooming by limiting the CRT beam current to an arbitrarily selected acceptable level. There are also white compression circuits which limit peak white video signals resulting in severe signal compression or "white crushing" as the beam current approaches the limit. Most prior art video compression techniques have one or more drawbacks and are often characterized by a "washed out" appearance of the video display.
Another aspect of video enhancement is generally referred to as peaking or transient improvement. Peaking is performed by sharpening video transitions, i.e. the edges of video images, to emphasize the transition. Video peaking is considered to be beneficial in many situations but may be detrimental, especially in darker areas of the display. In accordance with the present invention, video peaking may be accomplished simultaneously with white compression.